Ride height setting based on transfer case setting

Abstract

In vehicles having drive wheel selections, accessed for example through a transfer case, drive wheel settings are used to determine a desired vehicle ride height at which the vehicle is maintained by a vehicle suspension control system. Preferably, both vehicle speed and transfer case setting are combined to determine the desired vehicle ride height. With two wheel drive selected, the desired vehicle ride height is set to a low ride height which provides the most aerodynamic airflow for the vehicle. However, if four wheel drive is selected, the speed is checked to determine the desired vehicle ride height. If four wheel drive (automatic four wheel drive) is selected, low ride height is still selected for speeds in excess of a first defined speed. For speeds at or below the first defined speed, a high ride height approximately 1 inch above the low ride height is set for the desired ride height. If four wheel drive low is selected, typically in contemplation of off-road operation, a higher still ride height or off-road ride height approximately 1 inch above high ride height is set for the desired ride height.

What is claimed is: 
     
       1. A method for controlling the ride height of a vehicle having selectable drive wheels including at least a two wheel drive setting and a four wheel drive setting for said vehicle, said method comprising the steps of: sensing the speed of the vehicle;   selecting the drive wheel setting of the vehicle; and   selecting a desired vehicle ride height at which the vehicle is maintained by combining the drive wheel setting and the speed of the vehicle.   
     
     
       2. A method for controlling the ride height of a vehicle as claimed in claim 1 wherein said step of selecting the drive wheel setting of the vehicle comprises the step of automatically selecting the drive wheel setting of the vehicle. 
     
     
       3. A method for controlling the ride height of a vehicle as claimed in claim 1 wherein said step of selecting the drive wheel setting of the vehicle comprises the step of manually selecting the drive wheel setting of the vehicle. 
     
     
       4. A method for controlling the ride height of a vehicle having selectable drive wheels including at least a two wheel drive setting and a four wheel drive setting for said vehicle and at least two selectable ride heights, a low ride height and a high ride height, said method comprising the steps of: sensing the speed of the vehicle;   selecting the drive wheel setting of the vehicle; and   selecting a desired vehicle ride height at which the vehicle is maintained based on the drive wheel setting by combining the drive wheel setting and the speed of the vehicle by performing the steps of: setting the desired vehicle ride height to the low ride height for the two wheel drive setting;   setting the desired vehicle ride height to the low ride height for the four wheel drive setting if the speed of the vehicle is greater than a first defined speed; and   setting the desired vehicle ride height to the high ride height for the four wheel drive setting if the speed of the vehicle is less than said first defined speed.     
     
     
       5. A method for controlling the ride height of a vehicle as claimed in claim 4 further comprising the step of setting said first defined speed to approximately 58 miles per hour. 
     
     
       6. A method for controlling the ride height of a vehicle as claimed in claim 4 wherein three drive settings, a two wheel drive setting, a four wheel drive setting and a low four wheel drive setting, are selected, three ride heights, a low ride height, a high ride height and an off-road ride height higher than said high ride height, are selected, and said step of combining the drive wheel setting and the speed of the vehicle to select a desired vehicle ride height further comprises the steps of: setting the desired vehicle ride height to the low ride height for the low four wheel drive setting if the speed of the vehicle is greater than a second defined speed; and   setting the desired vehicle ride height to the off-road ride height for low four wheel drive setting if the speed of the vehicle is less than said second defined speed.   
     
     
       7. A method for controlling the ride height of a vehicle as claimed in claim 6 further comprising the step of setting said second defined speed to approximately 30 miles per hour. 
     
     
       8. A method for controlling the ride height of a vehicle having a transfer case for selecting between at least a two wheel drive setting and a four wheel drive setting for said vehicle, said method comprising the steps of: sensing the speed of the vehicle;   sensing the drive setting of the transfer case; and   selecting a desired vehicle ride height at which the vehicle is maintained by combining the drive setting of the transfer case and the speed of the vehicle.   
     
     
       9. A method for controlling the ride height of a vehicle having a transfer case for selecting between at least a two wheel drive setting and a four wheel drive setting for said vehicle and at least two selectable ride heights, a low ride height and a high ride height, said method comprising the steps of: sensing the speed of the vehicle;   sensing the drive setting of the transfer case; and   selecting a desired vehicle ride height at which the vehicle is maintained in response to the drive setting by combining the drive setting of the transfer case and the speed of the vehicle by preforming the steps of: setting the desired vehicle ride height to the low ride height for the two wheel drive setting of the transfer case;   setting the desired vehicle ride height to the low ride height for the four wheel drive setting of the transfer case if the speed of the vehicle is greater than a first defined speed; and   setting the desired vehicle ride height to the high ride height for the four wheel drive setting of the transfer case if the speed of the vehicle is less than said first defined speed.     
     
     
       10. A method for controlling the ride height of a vehicle as claimed in claim 9 further comprising the step of setting said first defined speed to approximately 58 miles per hour. 
     
     
       11. A method for controlling the ride height of a vehicle as claimed in claim 9 wherein said transfer case provides for selecting between a two wheel drive setting, a four wheel drive setting and a low four wheel drive setting, three ride heights, a low ride height, a high ride height and an off-road ride height higher than said high ride height, are selected, and said step of combining the drive setting of the transfer case and the speed of the vehicle to select a desired vehicle ride height further comprises the steps of: setting the desired vehicle ride height to the low ride height for the low four wheel drive setting if the speed of the vehicle is greater than a second defined speed; and   setting the desired vehicle ride height to the off-road ride height for low four wheel drive setting if the speed of the vehicle is less than said second defined speed.   
     
     
       12. A method for controlling the ride height of a vehicle as claimed in claim 11 further comprising the step of setting said second defined speed to approximately 30 miles per hour.